Method for making a friction welded article

ABSTRACT

First and second metal components to be joined at opposed interface surfaces by friction welding, the first component having greater hot strength than the second component, are friction welded by first shaping the interface surface of the first higher hot strength component prior to friction welding so that initial contact during friction welding is at the peripheral areas of the contacting surfaces. In one form, such shaped surface is in the form of a depression concave into the first component. The walls of the depression are disposed at an angle in the range of about 1* - 10* in respect to a plane normal to the friction welding axis of rotation.

United States Patent [1 1 Rajala Oct. 2, 1973 METHOD FOR MAKING AFRICTION WELDED ARTICLE [75] Inventor: Ronald G. Rajala, Loveland, Ohio[73] Assignee: General Electric Company,

Cincinnati, Ohio [22] Filed: Dec. 21, 1971 [21] Appl. No.2 210,386

FOREIGN PATENTS OR APPLICATIONS 572,789 10/1945 Great Britain 29/4703Primary Examiner-J. Spencer Overholser Assistant Examiner-Robert J.Craig Attorney-Derek P. Lawrence et al.

[57] ABSTRACT First and second metal components to be joined at opposedinterface surfaces by friction welding, the first component havinggreater hot strength than the second component, are friction welded byfirst shaping the interface surface of the first higher hot strengthcomponent prior to friction welding so that initial contact duringfriction welding is at the peripheral areas of the contacting surfaces.In one form, such shaped surface is in the form of a depression concaveinto the first component. The walls of the depression are disposed at anangle in the range of about 1 10 in respect to a plane normal to thefriction welding axis of rotation.

4 Claims, 2 Drawing Figures METHOD FOR MAKING A FRICTION WELDED ARTICLEBACKGROUND OF THE INVENTION The invention herein described was made inthe course of or under a contract, or a subcontract thereunder, with theUnited States Department of the Air Force.

Friction welding, various forms of the method and apparatus for whichhave been widely discussed in the literature, is a solid state processfor joining two components which are moved either relatively rotationalor reciprocally with respect to one another. When such moving componentsare pressed one against the other with sufficient force, heat generatedby friction between the components produces the friction welded joint.

Generally the relatively moving surfaces of the components at which thefriction welded joint is to be produced are matched in shape one withthe other. In the more simple forms, such surfaces are planar andparallel.

If the hot strength characteristics of both components are substantiallythe same and the areas of the surfaces to be joined are substantiallyequal, upsetting of each component will be substantially the same andfriction welding can occur without significant problems. However, ifunder such size conditions the hot strength characteristics of one ofthe two components are greater than the other, preferential upsettingwill occur in the weaker component. This sometimes occurs prior to thegeneration of sufficient frictional heat to provide a friction weldedbond between the two components. One reported method for overcoming suchpreferential upset is to provide the lower hot strength component with agreater interface area than the stronger component in a flat, butt-weldconfiguration. Another reported approach to a solution to this probleminvolves shaping of the interface surface of the component with thehigher hot strength so that it forms an apex, truncated cone, rounded orother convex interface when opposed to the flat interface surface of thelower hot strength component. However, it has been found that theseconfigurations generate less frictional heat, and when generated, itinitiates and builds at the central contact area. This tends to favorupset of the lower hot strength material.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide an improved method for friction welding componentsone of which has not strength properties greater than the other.

Another object is to provide such a method by improved shaping of theinterface surface of the component having greater hot strengthproperties.

These and other objects and advantages will be more clearly understoodfrom the following detailed description and the drawing, all of whichare meant to be representative of rather than limiting on the scope ofthe present invention.

The present invention provides a method for friction welding first andsecond metal components each of which has an interface surface to beopposed one to the other during friction welding. The first of suchcomponents has hot strength properties greater than the second. Ingeneral, the method includes shaping the interface surface of the firstcomponent so that initial contact between the first and second interfacesurfaces will be at such surfaces peripheral area. In one specific form,the first surface is shaped in the form of a depression, concave intosuch component. The walls of the depression are disposed in general atan angle in the range of about l 10 in respect to a plane normal to thefriction welding axis of rotation. The interface surfaces of the firstand second components are positioned in spaced apart, opposedrelationship and then friction welding of such components is conductedat their interface surfaces.

BRIEF DESCRIPTION OF THE DRAWING FIG. is a fragmentary, sectionalillustration of a pair of solid metal components with their interfacesurfaces in spaced apart, opposed relationship prior to friction weldingaccording to the present invention; and

FIG. 2 is a fragmentary, sectional view of a pair of tubular metalcomponents in the same relationship as in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Illustrated in FIGS. 1 and 2are relatively simple arrangements of two metallic components,substantially of the same dimensions, positioned prior to frictionwelding. First component 10 having an interface surface 12 has hotstrength properties greater than second component 14 which includesinterface surface 16. In simple form, these can be a pair of round barsor a pair of tubular members to be joined by friction welding at theirrespective interface surfaces 12 and 16.

For practice of one form of the method of the present invention,interface surface 12 of first component 10 is shaped in the form of adepression, concave into the first component. The walls of thedepression are disposed preferably at an angle A in the range of about l10 in respect to a plane normal to the friction welding axis of rotationrepresented by centerline l8. During friction welding, one or both ofthe first and second components l0 and 14 are rotated about frictionwelding axis 18 to provide different relative movement between thecomponents at their respective interfaces 12 and 16. During frictionwelding, the interface surfaces of the first and second components arepressed one on the other with a force sufficient to generate frictionalheat adequate to weld the metal components at their interface surfaces.

It has. been recognized that shaping the interface portion of the higherhot strength component in a manner, for example convex, such that itscontact with an opposed surface of the lower hot strength component isgenerally at their peripheral areas, rather than their central areas,results in generally balanced or equal upset of both components duringfriction welding. At the central areas, relative rotational speedbetween the two opposed surfaces is much lower than at the peripheralareas. Hence lower frictional heat is generated. This results in moredifficult friction welding which, when it occurs, favors upset of thelower hot strength material. The method of the present inventioncomprises shaping the interface portion of the higher hot strengthmaterial so that, when pressed into contact with an-opposed surfaceduring friction weldlng, initial contact occurs at the peripheral areasof the contacting surfaces.

'rli nri f-riifc'fioN WELIDiNo oXTA cry of the contacting surfacesduring friction welding. This results in significantly improved frictionwelding operation.

Specimen diam. (in.) Cast alloy 1 Total upset Weld Upset interfaceenergy, pressure,

Cast Wrought geometry k. lb. it./in. k.s.i. Cast Wrought Total 48 50Butt 235 58 004 092 096 50 50 Truncated cone, 220 58 050 099 149 50 50Concave 220 58 085 109 194 50 50 Convex 5... 220 58 016 078 094 1. 68 1.85 Convex 3 215 87 140 193 .333 1. 68 1. 85 Truncated con 215 87 100 173273 1. 71 1. 85 Concave 2 215 87 180 221 401 45 50 Concave 5 220 53 16945 50 Concave 7. 5 230 53 199 45 50 Concave 2. 5 230 53 204 45 .50Concave 1. 5 230 53 .205

1 Higher hot strength.

As used in the tables herein, klb. ft. means thou{ sands of foot poundsand ksi means thousands of pounds per squrae inch, El" means elongation"and R.A. means reduction in area. The wrought alloy was a nickel basesuperalloy sometimes referred to as Rene 95 alloy. The cast alloy inTable I and identified in Table II as Cast B was a nickel basesuperalloy sometimes referred to as Rene 120. The following Table 11gives high temperature tensile properties of these alloys along withanother cast nickel base superalloy, identified as Cast A and sometimesreferred to as Rene 80 alloy.

TABLE II Tensile Data 0.2% Temp. Ultimate Yield El R.A. Alloy ("F) (ksi)(ksi) Wrought 1800 35 26 31 49 Cast A 1800 5 8 4O 14 24 Cast B i800 7250 3 5 Wrought 2000 14 8 59 96 Cast A 2000 25 12 13 Cast B 2000 37 30 2l The significant difference in hot strength characteristics is to benoted between the wrought alloy and cast alloy B. Not as significant adifferent in hot strength exists between the wrought alloy and castalloy A. Accordingly, it was found that the practice of the method ofthe present invention was not necessary in their friction welding in theconfigurations tested.

The data of the above Table 1 show the significantly improved balance inupset and total upset characteristices'which result from practice of thepresent invention when significant differences in hot strength exists.Comparison of the approximately Va inch diameter 'specimens of examples1 through 4 show a relatively balanced upset between the cast andwrought materials, and an improved total upset for example 3 within thescope of the present invention. Note the high degree of unbalance andlower total upset in examples 1, i 2 and 4. Similarly, in theapproximately 1 96 diameter specimens of examples 5 through 7, the samesignificant improvement is shown for example 7 according to the presentinvention. Examples 8 through 1 1 represent other tests, on cast alloyinterface geometry, according to practice of this invention, disposed atangles in the range of about 1 in respect to a plane normal to thefriction welding axis of rotation.

Thus, a slight amount of relief in the central contact area of thesignificantly higher hot strength material is sufficient to concentratefrictional heat at the periph- As a result of these evaluations, it wasrecognized that with the interface depression at an angle of less thanabout 1", too little relief is afforded to direct the area of heatgeneration toward the peripheral area. In addition, with such anglegreater than about 10, the total amount of upset required to frictionweld would be excessive. For example, for a 1 94 inch diameter specimem,it was found that there is a 0.017 inch drop for each degree of angle.Thus, for greater than a 10 angle, it would be necessary to upset thehigher hot strength material more than 0.17 inch in order to frictionweld to the lowest point in the depression. Because of the substantiallybalanced upset which results from practice of the present invention,total upset would have to be greater than about 0.35 inch, which isexcessive for practical applications.

AlToii ghTh e present invention has been described in connection withspecific examples and embodiments, it will be understood by thoseskilled in the art of metallurgy and friction welding the modificationsand variations of which the present invention is capable.

What is claimed is:

1. In a method for friction welding first and second metal components,each having an interface surface to be opposed one to the other duringfriction welding, the first component having hot strength propertiesgreater than the second component, the steps of:

shaping the interface surface of the first component in the form of adepression concave into the first component, the walls of the depressionbeing disposed at an angle in the range of between 1 10 in respect to aplane normal to the friction welding axis of rotation and in respect tothe interface surface of the second component so that the initialcontact between the first and second interface surfaces will be at theperipheral areas of such surfaces; positioning the interface surfaces ofthe first and second components in spaced-apart, opposed relationship;and then friction welding the first and second metal components at theirinterface surfaces.

2. The method as in claim 1 in which the first and second components aretubular in shape.

3. The method as in claim 1 in which each component is a nickel basesuperalloy.

4. The method of claim 3 in which The first component is a castsuperalloy structure and the second component is a wrought superalloystructure.

2. The method as in claim 1 in which the first and second components aretubular in shape.
 3. The method as in claim 1 in which each component isa nickel base superalloy.
 4. The method of claim 3 in which The firstcomponent is a cast superalloy structure and the second component is awrought superalloy structure.